He said: "Some common characteristics of a cannabis growing operation are blocked or blacked-out windows, people coming and going at strange times of the day and bags or boxes of equipment being moved into rented properties.

"It seems like the culprits were tapping into the electricity supply, which also poses a real threat to houses nearby.

"The energy company had been contacted and were with us when we raided the house."

Anyone with information about the cultivation of drugs should contact their nearest Safer Neighbourhoods team or Crimestoppers anonymously on 0800 555 111.

* There has been a big rise in the number of cannabis factories found in what look like ordinary suburban houses in recent months.

Organised criminal gangs, many from south-east Asia, are responsible for the rise, police believe.

The Home Office says the high detection rates are an 'encouraging sign'.

Law enforcement agencies from all over the country have been discussing ways to clamp down more effectively on the problem.